This thesis explores aspects of what happened to the state Church of Sweden during the rise of the importance of public opinion and the evolution of the democratic nation state. Denmark provides the most well known Nordic example of how an old state Church became a democratic Folk (i.e. National) Church during this general transition. By comparing the Swedish with the Danish case, this study elucidates the less well known Folk Church ideology in Sweden. In Denmark a strong agrarian movement influenced by revivalism managed to take hold of public opinion making the state Church a part of the Danish national identity. Such a movement never appeared in the more industrialised Sweden. Instead a secular working class movement took hold of public and national opinion. The investigation is focused upon Harald Hallén (1884-1967), a pastor and a Social Democratic Member of Parliament. Lacking the revival elements of the Danish nationalism Hallén found that in order to get a Folk Church accepted within the secular Working class movement, it had to rest upon the heritage of the Enlightenment. Hallén regarded the Church as an expression of common ethical values within the Swedish nation. The Folk Church was supposed to strengthen existing ideals for a righteous socialist society by delivering the message of the Kingdom of God. Hallén strove to make the Church more democratic in order to express this ethical folk religion. Social Democratic nationalism became the dominant factor in Swedish political life between 1905 and 1933. The period was characterised by conflicts. First Hallén and those whom he represented fought against the Youth Church movement, which strove to establish another Folk Church ideology, by supporting the Swedish King against the rise of political Democracy. Later on, within his own Social Democratic party, Hallén fought his battle against the Marxist view of the state Church as a simple reflection of the dominant class. Hallén was in line with the political development, which resulted in a period of solid Social Democratic nation building from the 1930s onwards. From that decade on the Folk Church ideology of Hallén was established.